nfs.systemd(7) — Linux manual page


NFS.SYSTEMD(7)        Miscellaneous Information Manual        NFS.SYSTEMD(7)

NAME         top

       nfs.systemd - managing NFS services through systemd.

SYNOPSIS         top


DESCRIPTION         top

       The nfs-utils package provides a suite of systemd unit files which
       allow the various services to be started and managed.  These unit
       files ensure that the services are started in the correct order, and
       the prerequisites are active before dependant services start.  As
       there are quite  few unit files, it is not immediately obvious how
       best to achieve certain results.  The following subsections attempt
       to cover the issues that are most likely to come up.

       The standard systemd unit files do not provide any easy way to pass
       any command line arguments to daemons so as to configure their
       behavior.  In many case such configuration can be performed by making
       changes to /etc/nfs.conf or other configuration files.  When that is
       not convenient, a distribution might provide systemd "drop-in" files
       which replace the ExecStart= setting to start the program with
       different arguments.  For example a drop-in file systemd/system/nfs-
       mountd.service.d/local.conf containing
              ExecStart= /usr/sbin/rpc.mountd $RPCMOUNTDOPTS
       would cause the nfs-mountd.service unit to run the rpc.mountd program
       using, for arguments, the value given for RPCMOUNTDOPTS in
       /etc/sysconfig/nfs.  This allows for seamless integration with
       existing configuration tools.

   Enabling unit files
       There are three unit files which are designed to be manually enabled.
       All others are automatically run as required.  The three are:
              This should be enabled on any host which ever serves as an NFS
              client.  There is little cost in transparently enabling it
              whenever NFS client software is installed.

              This must be enabled to provide NFS service to clients.  It
              starts and configures the required daemons in the required

              The blkmapd daemon is only required on NFS clients which are
              using pNFS (parallel NFS), and particularly using the
              blocklayout layout protocol.  If you might use this particular
              extension to NFS, the nfs-blkmap.service unit should be

       Several other units which might be considered to be optional, such as
       rpc-gssd.service are careful to only start if the required
       configuration file exists.  rpc-gssd.service will not start if the
       krb5.keytab file does not exist (typically in /etc).

   Restarting NFS services
       Most NFS daemons can be restarted at any time.  They will reload any
       state that they need, and continue servicing requests.  This is
       rarely necessary though.

       When configuration changesare make, it can be hard to know exactly
       which services need to be restarted to ensure that the configuration
       takes effect.  The simplest approach, which is often the best, is to
       restart everything.  To help with this, the nfs-utils.service unit is
       provided.  It declares appropriate dependencies with other unit files
       so that
              systemctl restart nfs-utils
       will restart all NFS daemons that are running.  This will cause all
       configuration changes to take effect except for changes to mount
       options lists in /etc/fstab or /etc/nfsmount.conf.  Mount options can
       only be changed by unmounting and remounting filesystem.  This can be
       a disruptive operation so it should only be done when the value
       justifies the cost.  The command
              umount -a -t nfs; mount -a -t nfs
       should unmount and remount all NFS filesystems.

   Masking unwanted services
       Rarely there may be a desire to prohibit some services from running
       even though there are normally part of a working NFS system.  This
       may be needed to reduce system load to an absolute minimum, or to
       reduce attack surface by not running daemons that are not absolutely

       Three particular services which this can apply to are rpcbind,
       idmapd, and rpc-gssd.  rpcbind is not part of the nfs-utils package,
       but it used by several NFS services.  However it is not needed when
       only NFSv4 is in use.  If a site will never use NFSv3 (or NFSv2) and
       does not want rpcbind to be running, the correct approach is to run
              systemctl mask rpcbind
       This will disable rpcbind, and the various NFS services which depend
       on it (and are only needed for NFSv3) will refuse to start, without
       interfering with the operation of NFSv4 services.  In particular,
       rpc.statd will not run when rpcbind is masked.

       idmapd is only needed for NFSv4, and even then is not needed when the
       client and server agree to use user-ids rather than user-names to
       identify the owners of files.  If idmapd is not needed and not
       wanted, it can be masked with
              systemctl mask idmapd
       rpc-gssd is assumed to be needed if the krb5.keytab file is present.
       If a site needs this file present but does not want rpc-gssd running,
       it can be masked with
              systemctl mask rpc-gssd

FILES         top


SEE ALSO         top

       systemd.unit(5), nfs.conf(5), nfsmount.conf(5).

COLOPHON         top

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